This invention relates to a color image processing apparatus which is suited for a photoelectric digital color copying apparatus which allows for full color copying, especially to a color image processing apparatus which controls the image forming processes by discriminating between a monochromatic document containing mostly black characters and a color document and provides outstanding color reproducibility and color balance adjustment operability.
Most photoelectric digital color copying apparatuses which allow for full color copying are configured to use a plurality of image forming processes for obtaining desired color copies.
When reproducing, for example, a desired color document using three colors as color copying developers, yellow Y, Magenta M, and cyan C, or the three colors plus black BK, the target color document can be copied by repeating the image forming process three or four times at most to superpose the developers.
When a color image processing apparatus which uses the superposition method for copying a color document is to be used, the image forming process repeat count should be controlled according to the color document.
When only one of Y, M, and C is to be used for copying a color document, the color image can be developed using one developer, which allows the image forming process to be performed once. For copying another chromatic color or monochromatic color documents, the image forming process should be repeated as many as the number of necessary target colors.
For such a color image processing apparatus, therefore, it is an extremely important problem to detect the color information of a color document. It is comparatively simple to configure a color information discriminating means by increasing the circuit scale for accurately detecting a color document. However, this method causes an increase in cost and difficulties in miniaturizing the circuit substrate.
The present invention provides a color image processing apparatus which can definitely discriminate the color information of a color document without increasing the circuit scale in view of those problems.
In some of such color image processing apparatuses, the density adjustment is performed for each of R, G, and B as a color balance adjustment. For such a density adjustment, the color density of each of R, G, and B is increased or decreased.
When the color balance adjustment of such an apparatus is performed by increasing or decreasing one of the colors R, G, and B, portions, an original colored black may be colored differently and achromatic portions such as black characters may be colored with a chromatic color.
In view of the above problems, an object of the present invention is to realize a color image processing apparatus that prevents achromatic portions from being colored by the color balance adjustment. In such a color image processing apparatus, the color balance adjustment is generally performed in the progression where the color signals are in the form of Y, M, C, and BK just prior to turn out the signals to an image output apparatus (printer) .
FIG. 24 shows a schematic diagram of such a color image processing apparatus. In the figure, numeral 1 designates a scanner unit which optically reads a document image and outputs digital data for each of R, G, and B. Numeral 2 designates a color reproduction section which converts the read R, G, and B data to Y, M, C, and BK, which are recording toner colors, data. Numeral 3 designates a color balance adjusting section which performs a density adjustment for the Y, M, C, and BK data for each color as a color balance adjustment. Numeral 4 designates a printer unit which forms an image according to the color-balance adjusted Y, M, C, and BK data. For the color balance adjustment of such a color image processing apparatus, the density is increased or decreased for each of the colors Y, M, C, and BK.
There is a problem imposed by the color balance adjustment of such an apparatus that it is difficult for the operator to have a sense of color balance adjustment because the read R, G, and B data do not have a one-to-one correspondence with the outputted Y, M, C, and BK data. There is another problem that, since the gradation characteristics of each of the colors Y, M, C, and BK outputted by the printer are not uniform and the characteristics are complicated, the adjustment cannot be performed easily,
In view of the above problems, another object of the present invention is to realize a color image processing apparatus which allows for easy color balance adjustment.